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Hints, Tricks, & Notes
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The TinyTrak3 uses inverted TTL levels (0 & 5 volts) for serial communication, rather than true RS-232 levels (-12 & +12
volts). This may cause communication problems with some GPS receivers and computers, especially laptops. An RS-
232 level converter, such as a MAX232, may be used, but the Allow TTL serial should be enabled.
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TinyTrak3’s carrier detects circuit detects all audio energy, not just packet audio tones. Therefore, it will not transmit
over received voice audio. Be sure NOT to run an open squelch, as this will prevent all transmissions. The receiver
should be set for maximum volume.
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TinyTrak3 can be mounted in a case with a GPS, with a single DB-9 jack for PC configuring. To do this, wire the GPS
serial output through a 10K resistor before connecting to the solder side of pin 2 of TinyTrak3’s DB-9 connector. This
way, with no PC connected, the GPS serial data will feed into the TinyTrak3, but when the PC is connected, the PC will
over-power the GPS during configuration.
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If you enter a small Transmit Every value, you may find it difficult to write new configuration settings, since the TinyTrak3
will be too busy transmitting to monitor serial. To resolve this, turn the R9 pot such that the CD LED turns on. This will
prevent TinyTrak3 from transmitting, and all the new settings can then be written.
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TinyTrak3 was designed for hand held radios. Some mobile radios require more audio drive than TinyTrak3 puts out. If
audio levels are too low, even with the R6 pot set to maximum, consider replacing the 220K R5 with a 100K resistor.
This should allow for about double the audio range. R5 can even be replaced with a jumper (0 ohm resistor) for
maximum audio.
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TinyTrak3 can be affected by local RF energy. To avoid this, run the transmitter at low power and keep TinyTrak3 away
from the transmitting antenna. It may also help to use shielded cables and case, and toroid filters.
